Recently, printing using water-based ink for preparing a hard copy at high speed has been performed in offset printing and letterpress printing and importance is being attached to the characteristics of a recording medium. Particularly, with the technical advance of ink jet printers, it has become possible to obtain clear images and superior print quality. At the same time, a demand exists for a recording medium having higher characteristics in order to further improve the print quality. To meet this demand, various recording media have been developed.
On the other hand, the use of water-based ink jet printers has spread and such printers are in use also for advertisement such as posters. In such a use, not only such recording characteristics as high image quality and high recording density are needed, but also it is necessary to keep images clear in long-term bulletin or storage. Heretofore, water-based dye inks superior in color developing property have been used as inks for ink jet printers. Generally, however, water-based dye inks are apt to fade when exposed to light and the clearness thereof is lost with the lapse of time. Thus, water-based dye inks have so far been unsuitable for long-term bulletin or storage. In an effort to solve such a problem, the number of printers and plotters using water-based pigment inks superior in light resistance is now increasing.
However, water-based pigment inks are different in characteristics from water-based dye inks for example because of the fact that the pigments used in the water-based pigment inks are particulate. Consequently, recording media to be respectively used exclusively for such two types of inks have been provided and at present there is scarcely any recording medium suitable for both types of inks.
Generally, recording media for pigment inks are designed to enhance their ink absorbing property, while in the case of recording media for dye inks, the ink absorbing property thereof is set lower than that of the recording media for pigment inks, but instead there is selected a suitable ink fixing agent. Thus, water-based dye inks and water-based pigment inks have characteristics contrary to each other, so if inks and recording media are used in erroneous combinations, there eventually are obtained only recorded matters impaired in quality such impracticable image density or blotting. For example, when printing is performed using pigment ink onto a conventional recording medium for water-based dye ink, the pigment ink is not absorbed and there occurs a phenomenon such as unevenness or cracking in the printed portion, thus giving rise to a problem in practical use.
Recording media for water-based ink are broadly classified into a gloss type high in the degree of gloss, a mat type low in the degree of gloss, and a plain paper type having a texture almost close to that of wood-free paper. Gloss type recording media are classified into a type using resin-coated paper used as a base of silver salt photographic printing paper and a type using paper. In both types, a fine particle diameter distribution is narrow and a coating layer can be formed using a pigment which can ensure transparency, making both absorbability and gloss compatible with each other. In case of recording something on a gloss type recording medium out of these recording media, the absorption of ink is slow because an ink receptive layer is formed on the recording medium with use of a fine pigment, and therefore the recording speed is decreased to a recording speed in a printer, thereby suppressing the occurrence of ink blotting. This eventually means that the printing speed is low and that therefore the printer capacity is not exhibited to a satisfactory extent.
Particularly, in the case of a mat type recording medium, since it is designed mainly for improving the ink absorbing property, there is used a pigment much larger in particle diameter than the pigment used in the gloss type, resulting in that the degree of gloss is made low. As a recording medium further improved in such excellent ink absorbing property there is known one wherein the surface of a paper base is subjected to a surface treatment for improving a solvent passing characteristic, thereby accelerating a rapid flow of liquid in a boundary region between an ink receptive layer and a paper base. Anyhow, since the mat type recording medium is large in the diameter of pigment particles, it is higher in ink absorbing speed than the gloss type and it is said that its recording speed in a printer can be set high. Recently, however, with the spread of digital cameras, the recording of full-color images has come to be performed not only for the gloss type but also for the mat type of recording media. Consequently, the amount of ink per unit area increases in comparison with that in recording monochromatic images, thus creating a demand for further improved ink absorbing characteristics. However, an attempt to meet this demand gives rise to the problem that there occur color tastes and blotting of various colors.
As noted above, under the present situation wherein a recording medium suitable for both water-based dye ink and water-based pigment ink, both being different in absorption characteristic, has not been provided yet, it may be effective to adopt a recording medium improved in recordability by forming plural ink receptive layers such as the one disclosed Patent Literature 1 or 2. However, a recording medium fully satisfactory in absorption characteristic for both water-based dye ink and pigment ink has not been provided yet.